Determine error matching pattern in catch?

In the catch statement you can use a switch/case statement to look for a specific error type. I have created an errors generator example that you can place into playgrounds to see the switch/case pattern in use.

/**
 Errors Example code by Sean Batson (MobileTen)
 */
import Foundation

enum GenericErrors: Error {
    case offline, certificates
}

extension GenericErrors: LocalizedError {
    var errorDescription: String? {
        switch self {
        case .offline:
            return "Server responded out of disk space"
        case .certificates:
            return "Certificates expired 24 hours ago"
        }
    }
}

enum ForumQuestionErrors: Error {
    case answered, none
}

extension ForumQuestionErrors: LocalizedError {
    var errorDescription: String? {
        switch self {
        case .answered:
            return "Question previously answered limit reached"
        case .none:
            return "Ok"
        }
    }
}

class Forums {
    let error = [offlineGenericError, certsGenericError, answeredForumError, noneForumError]
    func generateError() {
        let method = error[Int.random(in: 0..<error.count)]
        do {
            try method(self)()
        } catch {
            switch error {
            case is GenericErrors:
                print(error, error.localizedDescription)
            case is ForumQuestionErrors:
                print(error, error.localizedDescription)
            default:
                print(error, error.localizedDescription)
            }
        }
    }

    func offlineGenericError() throws {
        throw GenericErrors.offline
    }

    func certsGenericError() throws {
        throw GenericErrors.certificates
    }

    func answeredForumError() throws {
        throw ForumQuestionErrors.answered
    }

    func noneForumError() throws {
        throw ForumQuestionErrors.none
    }
}
let forum = Forums()
forum.generateError()